Solid-state Reaction Research Articles

Enhanced Quantum Efficiency via Co‐Substitution in Red‐Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra‐High Luminescence Saturation Threshold

AbstractIn order to obtain novel and more efficient red light‐emitting materials, a series of Sr2[Mg1−xLixAl5−xSixN7] : 0.01Eu2+ (SMAN‐xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co‐substitution of [Mg−Al]5+ by [Li−Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li−Si]5+ co‐substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li−Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li−Si]5+ co‐substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN‐0.1LS can achieve an ultra‐high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high‐power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN‐0.1LS. By measuring the pressure‐dependent luminescence of SMAN‐0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Multifunctional Near-Infrared Luminescence Performance of Nd3+ Doped SrSnO3 Phosphor

The phosphors with persistent luminescence in the NIR (near-infrared) region and the NIR-to-NIR Stokes luminescence properties have received considerable attention owing to their inclusive application prospects in the in vivo imaging field. In this paper, Nd3+ doped SrSnO3 phosphors with remarkable NIR emission performance were prepared using a high temperature solid state reaction method; the phase structure, morphology, and luminescence properties were discussed systematically. The SrSnO3 host exhibits broadband NIR emission (800–1300 nm) with absorptions in the near ultraviolet region. Nd3+ ions emerge excellent NIR-to-NIR Stokes luminescence under 808 nm laser excitation, with maximum emission at around ~1068 nm. The concentration-dependent luminescence properties, temperature dependent emission, and the luminescence decay curves of Nd3+ in the SrSnO3 host were also studied. The Nd3+ doped SrSnO3 phosphors exhibit exceptional thermal stability; the integrated emission intensity can retain approximately 66% at 423 K compared to room temperature. Most importantly, NIR persistent luminescence also can be observed for the SrSnO3:Nd3+ samples, which is in the first and second biological windows. A possible mechanism was proposed for the persistent NIR luminescence of Nd3+ based on the thermo-luminescence spectra. Consequently, the exciting results indicate that multifunctional NIR luminescence has been successfully realized in the SrSnO3:Nd3+ phosphors.

Antithermal-Quenching Near-Infrared Emitting Lu2SrAl4SiO12:Cr3+ Garnet-Type Phosphor for High-Resolution Nonvisual Imaging.

Near-infrared (NIR) light allows fast and nondestructive detection with deep penetration into biological tissues and is widely used in food inspection, biomedical imaging, night vision security, and other fields. Cr3+-doped NIR first region (NIR-I) phosphors have many interesting features that have attracted a lot of attention recently. However, practical issues, such as low photoluminescence quantum efficiency and poor thermal stability, need to be addressed. We synthesized Cr3+-doped Lu2SrAl4SiO12 garnet-type phosphors using a high-temperature solid-state reaction method. Under blue-light (@ 430 nm) excitation, the phosphors exhibited broadband NIR-I emission in the range of 600-1000 nm, with an emission peak at 710 nm. This system is unique, as the emission had multipeak sharp-line superposition and the Cr3+ ions were situated in a relatively strong crystal field environment, as opposed to a weak crystal field environment for other matrix. The optimal doping content of Cr3+ ions was 2 mol %, and its internal quantum efficiency was ∼76.8%. Surprisingly, this NIR phosphor showed an antithermal quenching effect, and the integrated luminescence intensity of NIR-I emission measured at 573 K was 206.3% of that measured at 303 K. We found that the antithermal quenching of NIR-I luminescence was caused by the extremely low thermal expansion coefficient and rigid structure of the Lu2SrAl4SiO12 matrix in the temperature range, as well as the weakening of electron-phonon coupling with increasing temperature. The optimized phosphor was packaged with a blue chip into a NIR phosphor-converted light-emitting diode device. The light source device showed an output power of 119.02 mW and an electro-optical conversion efficiency of 11.02% under a driving current of 300 mA. The application potential of this NIR phosphor was demonstrated in the field of high-resolution nondestructive imaging.

Copper Versatility in Hydroxyapatite: Valence States, Clusters, and Optical Absorption Properties.

The solid-state reaction between a stoichiometric hydroxyapatite (HA) and CuO at temperatures above 1100 °C produces pure Cux-HA phases for x ≤ 0.7 with the general formula Ca10CuIx(PO4)6(OH)2-xOx. The Cu atoms are located at the center of the hexagonal tunnels between two hydroxyl ligands, as determined by Fourier analysis based on XRD data. During heat treatment, the reduction of Cu2+ ions into Cu+ is concomitant with the stabilization of copper in HA in the hexagonal tunnel. The incorporation of monovalent copper within the apatite, as revealed by XANES spectroscopy, explains the violet color of the samples. The incorporation of Cu+ ions, by substitution of a hydrogen atom by copper(I), results in the formation of linear O-Cu-O chains where the majority of which are isolated for x ≤ 0.3. In addition, the EXAFS investigation showed, thanks to the linear geometry of these clusters that results in multiple diffusion effects, the existence of [CuO]n chains with n ≥ 2, which only appear clearly for higher copper contents x ≥ 0.5. The strong covalency of the Cu-O bond in such a dumbbell configuration would lead to strong hybridization between the 3d and 4s orbitals of copper and the 2p orbitals of oxygen, as illustrated by ESR signals. In the case of Cu-doped HA prepared by coprecipitation and annealed at a lower temperature (T ≤ 600 °C), copper substitutes calcium according to the theoretical formula Ca10-xCux(PO4)6(OH)2, mainly at the Ca(2) site. This local environment is in line with the Jahn-Teller distortion induced by the Cu2+ ion (as evidenced by UV-vis-NIR, XPS, and XANES-EXAFS spectroscopy analyses) and also allows copper-copper interactions from one site to another, as observed by ESR spectroscopy. This versatility of copper in HA gives it optical properties that change from a violet color with near-IR absorption to a blue hue. In all cases, Cu-O-Cu interactions persist whatever the valence state, and heat treatment induces a redox phenomenon, with copper exchanging between two sites close to each other.

Synthesis of SrTiO3 nanoparticles for photocatalytic applications

Due to the heightened emphasis on environmental protection and the escalating demand for renewable energy sources, the potential applications of strontium titanate (SrTiO3) nanoparticles in photocatalysis have shown remarkable promise. With rapid advancements in technological capabilities, the standards for SrTiO3 photocatalytic materials have soared. Researchers have relentlessly delved into and innovated techniques for preparing strontium titanate powders, striving to yield nanocrystalline SrTiO3 that exhibits specific morphologies, high purity, superior dispersibility, and exceptional photocatalytic efficiency, while continually refining the properties of these powders. The paper encapsulates the advancements in preparation methodologies and photocatalytic attributes of perovskite SrTiO3 nanoparticles, encompassing diverse synthetic routes such as hydrothermal synthesis, sol-gel process, chemical precipitation, solid-state reaction, sonochemical technique, and composite modification strategies. The characteristics, merits, demerits, and prevailing challenges associated with each synthesis technique are thoroughly and analyzed. Ultimately, this review serves as a valuable reference and foundation for the synthesis, modification, and application of SrTiO3 nanoparticle photocatalysts, fostering their development and practical implementation in environmental remediation and renewable energy technologies.

Impact of low-grade iron ore on sintering reactions: Rapid heating experiments and thermodynamic modeling

BackgroundSinter is a primary feedstock for blast furnace-based ironmaking. Recently, the proportion of low-grade iron ore, which contains a high amount of gangue (mainly SiO2), has been increasing in the sintering process. Therefore, the impact of increased SiO2 content on the quality of sinter needs to be clarified. MethodsIn this study, we designed a rapid-heating furnace to simulate the actual thermal profile of the sintering process. The effects of basicity values, sintering temperature, and atmosphere, on the microstructure and phase formation of the Fe2O3-CaO-SiO2 ternary mixtures during sintering reactions, are investigated using X-ray diffractometry and scanning electron microscopy. The experimental results are analyzed using CALPHAD-type computational thermodynamics. Significant findingsWe found that solid-state reactions dominate at the lower temperature of 1250 °C, while liquid-assisted sintering occurs at the higher temperature (1300 °C). As the SiO2 content in the sinter increases, the content of the calcium-ferrite bonding phase decreases, while the content of Ca2SiO4 and Fe2O3 increases. Regarding the role of the atmosphere, more calcium ferrite bonding phases form under a lower oxygen partial pressure compared to an ambient atmosphere, which facilitates the densification of the Fe2O3-CaO-SiO2 sinter. In addition, a guideline for sintering operation with low-grade iron ore is proposed.

Syntheses, structures and characterization of noncentrosymmetric MZnPO4 (M = K, NH4).

Two phosphates, KZnPO4 and NH4ZnPO4, were successfully synthesized using a solid-state reaction method and characterized via single-crystal X-ray diffraction. Both of their structures feature a three-way skeleton composed of isolated PO4 and ZnO4 tetrahedra, with K+/NH4+ cations occupying the spaces within the frameworks to balance charges. These compounds are isostructural and crystallize in the noncentrosymmetric P63 space group. Their structures were compared, revealing that non-centrosymmetric (NCS) KZnPO4 and NH4ZnPO4 exhibit second harmonic generation (SHG) responses of 0.4 × KDP and 1 × KDP, respectively. Furthermore, by combining the electronic structure and SHG density calculations, we examined the effects of ZnO4 tetrahedra on the SHG response of KZnPO4 and NH4ZnPO4.

Theoretical and experimental investigation of BaY2(MoO4)4:xSm3+ phosphors

In this paper, the novel BaY2(MoO4)4:xSm3+ phosphors with strong red emission and high thermal stabilization were prepared by a conventional method of high temperature solid state reaction in air atmosphere. Morphology, phase purity, element distribution, UV–Vis–NIR diffuse reflectance spectroscopy (DRS), and luminescence properties were investigated in detail. The crystal structure of the BaY2(MoO4)4 host was refined with the aid of the Rietveld refinement method by the GSAS program. The electronic band structure and phonon dispersion were performed using plane-wave density functional theory (DFT). The prepared BaY2(MoO4)4:Sm3+ phosphor exhibits excellent red emission under near-ultraviolet excitation. Strong red emission intensity and high thermal stability suggest potential application in backlighting or phosphor-covered white light-emitting diodes (pc-LEDs).

Effect of anisotropy field on the resonance frequency and reflection loss shift characteristics of barium hexaferrite ceramics

Abstract For this study, a modified barium hexaferrite based microwave and radar absorbing material was used. Synthesis and characterization of BaFe(12-2x)(MnTi)xO19 (0.1 ≤ x ≤ 1.0) have been prepared by solid state reaction method. The X-ray diffraction patterns reveal that all samples only crystallized into M-type barium hexaferrite after calcination at 1200 °C. Surface morphology images show that the hexagonal flake-like particle is formed at the initial stages of the Mn-Ti substitution level. The magnetic properties measurement reveals that the variation of magnetization values may vary based on preferable site occupation of Mn4+-Ti2+ cations to replace Fe3+ cations. The significant decrease in field coercivity (Hc) from 3.18 kOe to 0.51 kOe with the increase of Mn-Ti substitution affected the lowering values of field anisotropy (Ha). The maximum reflection loss (RL) positions of BaFe(12-2x)(MnTi)xO19 compositional series are shifted to lower frequency range following the Ha trendlines. The maximum RL value equals to 98.42% microwave absorption at 10.5 GHz has been obtained in x = 1.0 (BaFe10Mn0.5Ti0.5O19) composition.

Pyrolysis features of Dracaena draco lignocellulosic fibers: Kinetic and thermodynamic analysis at various heating rates through coats-redfern method

This study evaluated the thermokinetic and thermodynamic properties of Dracaena draco fibers (DDFs) through thermogravimetric analysis (TGA). The DDFs underwent non-isothermal heating in a nitrogen atmosphere, with 5, 10, and 20 °C/min heating rates starting at 20 °C and reaching 800 °C. TGA analysis demonstrated that the pyrolysis of DDFs took place in three clearly defined phases: dehydration, devolatilization, and solid biochar. The thermokinetic and thermodynamic properties were computed for the devolatilization phase of mass reduction. The Coats-Redfern technique employed twenty-one separate kinetic equations derived from four fundamental solid-state reaction processes. Out of all the diffusivity models (DMs), the Ginstlinge-Brounshtein (DM5), Jander (3D diffusion) (DM7), and Ginstling models (DM8) had the best fit, as indicated by their highest coefficient of regression values (R2 > 0.990) across all the three heating rates. The activation energy values found by the DM5, DM7, and DM8 models are 76.5, 82.32, and 76.47 kJ/mol, respectively, for the 5 °C/min heating rate. The thermodynamic variables, including the entropy, free energy, and enthalpy change, were calculated based on the kinetic data. The study’s findings are significant for evaluating the DDFs' potential as an energy source, constructing reactors, producing chemicals, and understanding the DDFs’s features for composite synthesis.

Ultralow Thermal Conductivity and Very High Seebeck Coefficient in Two-Dimensional TeSe2 Semiconductor.

Emerging chalcogenide-based two-dimensional (2D) materials possess various unique yet fully explored properties and are thus considered promising candidates for next-generation optoelectronic and energy conversion applications. Here, TeSe2 crystals with interesting thermoelectric features were synthesized using a simple solid-state reaction. High-resolution transmission electron microscopy reveals that TeSe2 stabilizes in a 2D atomic structure with helical chains, resembling 2D tellurene. The thermoelectric properties were measured from 2 to 390 K in a polycrystalline pellet, showing an ultralow thermal conductivity below 0.25 W m-1 K-1 and a very high positive Seebeck coefficient of up to 865 μV K-1. Particularly, the thermal conductivity shows a hysteresis effect upon temperature cycling, which is tentatively explained as cracks opening and partially closing. Optical measurements indicate that TeSe2 is a semiconductor with two bandgaps at 1.43 and 1.65 eV. These results highlight that TeSe2 is an intriguing 2D semiconductor with complex thermoelectric properties, which provides a platform to further study the interplay of emerging 2D structure, thermal, and electronic properties.

Synthesis of doped titanium-based lithium adsorbents with excellent stability and adsorption performance by solid state reactions

Titanium-based lithium-ion sieves (LTO) are often employed for lithium recovery from solutions due to their high adsorption uptake. To further reduce the Ti dissolution loss rate and enhance the adsorption performance of LTO, metal-doping was conducted using solid-state reactions in this work, and the effects of incorporated metal elements and doping amounts were investigated. The results indicated that, the doping of 5 % tungsten (W), zirconium (Zr) or cerium (Ce) significantly reduces the titanium dissolution rate from 1.52 % (without doping) to 0.77 %, 1.1 %, and 1.17 % respectively, while the doping of iron (Fe) and molybdenum (Mo) increases the Ti dissolution rate. Simultaneously, the dissolution rates of W, Zr, and Ce (0.15 %, 0.27 %, and 0.66 %) are also significantly lower than those of Fe and Mo (14 % and 24 %). In addition to the record-breaking reduction in the titanium dissolution rate, W doping also substantially enhances the saturated adsorption capacity of lithium to 48 mg g−1 (at 30 °C), 1.37 times that of the undoped LTO (35 mg g−1), demonstrating great potential for lithium recovery.

Comprehensive approach on La1-xPbxMnO3 (0.2 ≤ x ≤ 0.5) perovskites synthesized by solid state reaction technique

We have synthesized Pb concentrated La manganites La1-xPbxMnO3 (0.2 ≤ x ≤ 0.5) using solid state reaction route to investigate several physical properties such as structural, thermal, magnetic, electronic and elastic properties via both the experimental characterizations and the first principles calculations under the framework of density functional theory (DFT). The structures of the studied perovskites are examined by X-ray diffraction (XRD) pattern and also compared with the crystallographic data obtained by computations. The crystallization and formation of the studied phase of manganites are confirmed by analyzing the thermogravimetric (TG) curve. The temperature dependence of magnetization of all the samples exhibits a ferromagnetic metal phase with the Curie temperatures TC ranging from 334 to 338K. Although a metal-semiconductor transition is expected at around TC for the measurement of electrical resistivity with temperature but we observe semiconducting behavior because of the resistivity data started from room temperature. The calculated energy dispersion of all the manganites shows metallic conduction in conformity with the available experimental results. All the studied perovskites under investigation possess mechanical stability, malleability as well as anisotropy. The calculated Debye temperatures of all the Pb-doped La manganites show excellent correspondence with the other thermophysical parameters like melting point, phonon thermal conductivity and hardness as well.

Influence of calcium-doped on the conductivity of NASICON-type Na3Zr2Si2PO4 solid electrolyte

Sodium-ion solid electrolyte has many advantages such as high safety, good ionic conductivity, and strong chemical stability. NASICON-type Na3Zr2Si2PO4 solid electrolyte was prepared by high-temperature Solid State Reaction (SSR). X-ray Diffraction (XRD) show that the 20% excess addition of Na and P elements will reduce the formation of ZrO2 impurity phase and increase the ionic conductivity to 1.01×10−4 S cm−1. On the basis of this experiment, Ca was added to dope the Na site in Na3Zr2Si2PO4 with different contents. Electrochemical impedance spectroscopy (EIS) results show that the conductivity of Ca2+ doped Na2.7Ca0.15Zr2Si2PO4 is significantly increased to 1.53×10−4 S cm−1, the electronic conductivity is 3.99×10−8 S cm−1, and the activation energy is 0.32 eV. Cyclic voltammetry testing demonstrated stable chemical properties below to 5 V. Na | Na2.7Ca0.15Zr2Si2PO4 | Na3V2(PO4)3 battery still maintains a high capacity retention rate of 98.76% after 200 cycles at 25oC-0.2C. It indicating that the new 0.15molCa-doped Na2.7Ca0.15Zr2Si2PO4 has the highest electrical conductivity, which provides a new research idea for sodium-ion solid-state batteries and has great potential in solid-state battery applications.

Innovative dilute magnetic compositions for spin-electronics field: Room temperature ferromagnetism of Sr0.98Gd0.02Ti0.98X0.02O (X = Ru, Mn, Fe)

An interesting new dilute magnetic compositions have been synthesized by solid-state reaction from (Gd, Ru), (Gd, Mn) and (Gd, Fe) codoped SrTiO3 semiconductors. The X-ray diffraction (XRD) patterns of pure, (Gd, Ru), (Gd, Mn) and (Gd, Fe) codoped SrTiO3 samples verified the formation of cubic SrTiO3 structure. The morphological analysis using scanning electron microscope (SEM) showed that the addition of (Gd, Ru), (Gd, Mn) and (Gd, Fe) ions obviously effect on the grains size and shape of SrTiO3 powder. The band gap energy of SrTiO3 powder was found to be 3.22 eV, and when (Gd, Ru), (Gd, Mn) and (Gd, Fe) ions incorporated into its lattice a blue shift to 3.28, 3.29 and 3.295 eV were detected, respectively. The X-Ray photoelectron spectroscopy (XPS) analysis of (Gd, Mn) codoped SrTiO3 composition (best ferromagnetic sample) ruled out the presence of Gd and Mn metals and confirmed the existence of Gd3+ and Mn2+ oxidation states. The measured magnetic results indicated that (Gd, Ru), (Gd, Mn) and (Gd, Fe) dopants strongly advance the ferromagnetic nature of SrTiO3 structure. The H-M loop of (Gd, Mn) codoped SrTiO3 composition gives the best ferromagnetic order with detected saturation magnetization (MS), coercivity (HC) and retentivity (Mr) of 0.52 emu/g, 177 Oe and 0.054 emu/g, respectively. These outcomes established the promising room temperature ferromagnetic order of the fabricated compositions, especially Sr0.98Gd0.02Ti0.98Ru0.02O3 semiconductor for spin-electronics applications.

Effect of Rare Earth doping on Structural, Morphological, Optical, and Magnetic Properties of the Y1-x(Gd, Dy)xBaCuFeO5+δ (x = 0.2, 0.4, 0.6, and 0.8) Ceramics

The effect of the rare earth (RE) ion substitution on the structural, morphological, optical and magnetic properties of the Y1-xRExBaCuFeO5 (RE = Gd, Dy; x = 0.2, 0.4, 0.6, and 0.8) multiferroic compounds grown by the solid-state reaction is evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), reflectance spectroscopy techniques diffuse (UV-vis-NIR) and vibrating sample magnetometry (VSM). The results indicate that the RE substitution led to growth of single-phase materials, with a tetragonal structure and P4mm symmetry. The morphological analysis shows the formation of polycrystalline materials composed of grains of various shapes and sizes. Furthermore, the compositional analysis reveals that the materials do not present elements other than those used in the synthesis. The band gap (Eg) is tuned from 0.88 to 0.90 eV upon RE substitution. The magnetization curves obtained in the Zero-Field-Cooled/Field-Cooled (ZFC-FC) modes between 50 and 390 K, reveal a paramagnetic behavior, which could be attributed to the dominance exerted by the magnetic moments of the Gd/Dy ions.

Synthesis of cotton-like FeCoNi-Nd(OH)3 nanoparticles via reactive mechanical milling: Investigating chemical properties for cellular signaling applications

In this study, FeCoNi alloy nanoparticles were combined with Nd(OH)3 nanostructures to create unique cotton-like nanoparticles (C-NPs). These C-NPs were synthesized through an accessible, two-step reactive chemical milling process. The nanoparticles originated from a blend of metal chlorides (FeCl2, CoCl2, and NiCl2) and sodium (Na), used as a precursor in the reaction, within a SPEX milling apparatus. The Fe, Co, and Ni were maintained at equal weight percentages (1:1:1). Subsequently, NdCl3 and Na were utilized to facilitate the attachment of Nd(OH)3 nanostructures onto the FeCoNi nanoparticles through a solid-state reaction in the same SPEX milling setup. The Nd content was varied to investigate its effect on the integration of Nd(OH)3 onto the surface of CoNiFe nanoparticles. Electron microscopy revealed the formation of cotton-like nanoparticles, and the distribution of elements was identified using secondary ion mass spectrometry. The CoNiFe alloy and Nd(OH)3 phases were verified by X-ray diffraction analysis. These nanoparticles were internalized into cells via endocytosis, as observed in transmission electron microscopy images after incubation with the BT20 cell line (triple-negative breast cancer), likely due to interactions between –OH groups and the cell membrane. Following this, the cells containing C-NPs underwent photoluminescence studies, revealing two distinct emission peaks at 400 nm, and 486 nm. X-ray photoelectron spectroscopy indicated the presence of various heterostructures within the FeCoNi-Nd(OH)3 complex, which may be responsible for these emission properties.

Y, Yb, and Gd tri-doping on B-site of Ba(Zr, Ce)O3-δ with improved proton conduction performance

Perovskite-type proton conducting electrolytes are garnering significant attention due to its key role in protonic ceramic electrochemical cells (PCEC) and its application in hydrogen sensors (HS) used for metal melt measurements. Developing high proton conduction perovskite materials with good chemical stability is always a worldwide research focus. In this paper, Y, Yb and Gd triple-doping on B-site of BaCeO3-BaZrO3 solid solution were carried out to investigate the effect of gadolinium doping on the performance of protonic conducting electrolytes. BaZr0.1Ce0.7(Y0.5Yb0.5)0.2-xGdxO3-δ (x = 0, 0.1, 0.15 and 0.2), which were also referred as BZCYYbGdx (x = 0, 10, 15 and 20), were synthesized by solid-state reaction at 1600 °C for 10 h. It is found that BZCYYbGd15 has the highest proton conductivity and proton transfer number among the four prepared materials. The proton mobility of BZCYYbGd15 is 4.06 × 10−6 cm2/(Vꞏs) at 800 °C, which increases with an increased temperature. Its proton transfer number is higher than 0.9 at 500 °C under the atmosphere of PH2O = 0.018 atm. A moderate doping of gadolinium increases the temperature threshold for proton conduction. Proton, oxygen vacancy, electron hole and total conductivity activation energies of BZCYYbGd15 under the wet atmosphere are found to be 0.74, 1.58, 1.41 and 0.92 eV, respectively. Furthermore, the chemical stability of pellets is improved after gadolinium doping. This study provides a reference value for future research on high proton conduction electrolytes.

Investigation of Sr-substituted Ba1-xSrx(Zn1/3Nb2/3)O3 complex perovskites: structural, electrical and electrochemical properties

Herein we report the structural, dielectric and electrochemical properties of Ba1-xSrx(Zn1/3Nb2/3)O3 (BSZN, 0 ≤ x ≤1) solid solution synthesised by solid-state reaction. A complete substitutional solid solution was obtained, wherein the BSZN cubic perovskites of the space group of Pmm were obtained at x ≤ 0.6 while the pseudo-cubic phases were discernible at x > 0.6. The nano-sized crystallites, as determined by both Scherrer and Williamson-Hall analyses, supported the claim of large polyhedral grains of 0.1 to 0.3 μm by FE-SEM. Both ε′ and tan δ were found to vary consistently with increasing dopant concentration, except for an anomalous observation for the composition, x = 0.6 with the lowest tan δ of 0.0783 and the highest ε′ of 27.5. Such phenomenon could be attributed to the combined effects of larger grain size, higher relative density and stronger polarisation per molar volume. The impedance analysis revealed that these BSZN perovskites were of the negative temperature coefficient of resistance (NTCR) type. The combined plots of imaginary modulus (M″) and impedance (Z″) against frequency showed the short-range movement of localised charge carriers, suggesting a non-Debye-type relaxation process.

Enhanced optical, dielectric and transport properties in PVDF based (La0.5Bi0.5FeO3)0.5-(BaTiO3)0.5 composites

In this comprehensive study, we investigated PVDF composites incorporating LaBiFeO3-BaTiO3 (LaBiFO-BaTO) perovskite fillers, focusing on their structural, optical, dielectric, impedance, modulus and DC-conductivity properties. The fabrication involved precise preparation of LaBiFO-BaTO perovskite via solid-state reaction, ensuring phase purity conducive to composite integration. Using a solution casting method, PVDF films with varying LaBiFO-BaTO concentrations (5 %, 10 %, and 15 % wt) were successfully synthesized. XRD confirmed the synthesis of single-phase LaBiFO-BaTO and revealed structural modifications in PVDF composites, highlighting improved filler-matrix interactions at higher concentrations. Scanning electron microscopy and atomic force microscopy depicted the morphological evolution and surface roughness changes with increasing filler content. Optical studies indicated a red shift in absorption spectra with higher LaBiFO-BaTO concentrations, correlating with a decrease in the direct band gap energy of the composites. Electrical characterization demonstrated enhanced dielectric properties and impedance behaviour in PVDF/LaBiFO-BaTO composites, suggesting their suitability for applications in capacitors and optoelectronic devices. This systematic investigation provides valuable insights into optimizing PVDF-based composites for advanced functional materials. The composites exhibit enhanced dielectric permittivity at room temperature, attributed to space charge polarization and the high dielectric constant of LaBiFO-BaTO. Dielectric loss (tanδ) remains minimal (<0.1), decreasing with frequency, indicative of low energy dissipation suitable for high-frequency applications. Further the dielectric relaxation have been examined using Havrilak-Negami model. Impedance and modulus analyses reveal temperature-dependent behaviours, with reduced impedance and enhanced charge transfer kinetics in higher concentration composites. DC conductivity measurements demonstrate increased charge transport properties with temperature, influenced by thermally activated charge hopping mechanisms. Overall, PVDF/LaBiFO-BaTO composites show promising characteristics for capacitors, sensors, and optoelectronic devices, suggesting avenues for further optimization and broader application in advanced technologies.